A memory macro system may be provided. The memory macro system may comprise a first segment, a second segment, a first wl, and a second wl. The first segment may comprise a first plurality of memory cells. The second segment may comprise a second plurality of memory cells. The first segment may be positioned over the second segment. The first wl may correspond to the first segment and the second wl may correspond to the second segment. The first wl and the second wl may be configured to be activated in one cycle.
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1. An apparatus comprising:
a first segment comprising a first plurality of memory cells;
a second segment comprising a second plurality of memory cells wherein the first segment is positioned over the second segment;
a first bit line (bl) corresponding to the first segment wherein the first bl goes over the second segment in a flying bl scheme; #10#
a first word line (wl) corresponding to the first segment; and
a second wl corresponding to the second segment wherein the first wl and the second wl are configured to be activated in one cycle.
13. An apparatus comprising:
a first segment comprising a first plurality of memory cells;
a second segment comprising a second plurality of memory cells, wherein the first segment is positioned over the second segment;
a plurality of first bit lines (BLs) coupled to the first plurality of memory cells; #10#
a plurality of second BLs coupled to the second plurality of memory cells, wherein the first BLs goes over the second segment in a flying bl scheme;
a first multiplexer coupled between the plurality of first BLs and a first 10 circuit; and
a second multiplexer coupled between the plurality of second BLs and a second io circuit.
17. A method comprising:
providing a first segment comprising a first plurality of memory cells;
providing a second segment comprising a second plurality of memory cells wherein the first segment is positioned over the second segment;
providing a first bit line (bl) corresponding to the first segment wherein the first bl goes over the second segment in a flying bl scheme; #10#
receiving a memory address;
activating a first word line (wl) corresponding to the first segment based on the memory address;
activating a second wl corresponding to the second segment based on the memory address;
wherein the first wl and the second wl are activated in one cycle.
2. The apparatus of
4. The apparatus of
5. The apparatus of
a first Input Output (io) circuit corresponding to the first segment; and
a second io circuit corresponding to the second segment.
6. The apparatus of
a first plurality of multiplexers corresponding to the first segment; and
a second plurality of multiplexers corresponding to the second segment wherein the first plurality of multiplexers is positioned over the second plurality of multiplexers.
7. The apparatus of
a first plurality of multiplexers corresponding to the first segment; and
a second plurality of multiplexers corresponding to the second segment wherein the first plurality of multiplexers is positioned over the second plurality of multiplexers.
8. The apparatus of
9. The apparatus of
10. The apparatus of
a first bl tracking circuit corresponding to the first segment; and
a second bl tracking circuit corresponding to the second segment wherein a bl tracking scheme performed for the second segment by the second bl tracking circuit is faster than a bl tracking scheme performed for the first segment by the first bl tracking circuit.
11. The apparatus of
12. The apparatus of
14. The apparatus of
a first word line (wl) corresponding to the first segment; and
a second wl corresponding to the second segment wherein the first wl and the second wl are configured to be activated in one cycle.
15. The apparatus of
16. The apparatus of
18. The method of
19. The method of
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This application claims the benefit of U.S. Provisional Application No. 62/685,547 filed on Jun. 15, 2018, and entitled “SRAM MEMORY”, of which the entire disclosure is hereby incorporated by reference in its entirety.
Semiconductor memory is an electronic data storage device implemented on a semiconductor-based integrated circuit. Semiconductor memory has many different types, and has faster access times than other data storage technologies. For example, a byte of data can often be written to or read from semiconductor memory within a few nanoseconds, while access times for rotating storage, such as hard disks, is in the range of milliseconds. For these reasons, among others, semiconductor memory is used as a primary storage mechanism for computers to hold data that the computers are currently working on, among other uses.
Semiconductor memory devices include, for example, Static Random Access Memory (SRAM) cells and Dynamic Random Access Memory (DRAM) cells. DRAM memory cells have only one transistor and one capacitor, so it provides a high degree of integration. DRAM requires constant refreshing. Also, its power consumption and slow speed limit its use mainly for computer main memories. An SRAM cell, on the other hand, is bistable, meaning it can maintain its state indefinitely as long as an adequate power is supplied. SRAM can operate at a higher speed and lower power dissipation, so computer cache memories use SRAMs. Other applications include embedded memories and networking equipment memories. There are several types of SRAM cells (e.g., 6-transistor (6T) SRAM, dual port 8-transistor (8T) SRAM, etc.).
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
SRAM is a type of semiconductor memory that stores data in the form of bits using bistable circuitry without the need for refreshing. An SRAM cell may be referred to as a bit cell because it stores a bit of information. Memory arrays may include multiple bit cells arranged in rows and columns. Each bit cell in a memory array may include connections to a power supply voltage and to a reference voltage. Bit Lines (BLs) may be used for accessing a bit cell with a Word Line (WL) controlling connections to the BLs. A WL may be coupled to the bit cells in a row of a memory array with different WLs provided for different rows.
One type of semiconductor memory is a Dual-Port (DP) SRAM. A DP SRAM allows two memory accesses to occur at the same time, or at nearly the same time, respectively through two “ports”. The DP SRAM may comprise one or more banks of memory cells where each bank of memory cells comprises a plurality of memory cells arranged in rows and columns. Two word lines may correspond to the two ports and extend along each row, electrically coupling with each memory cell in the row. Two pair of Complementary BLs (CBLs) may correspond to the two ports and extend along each column electrically coupling with each memory cell in the column. The WLs of each port may allow access to the memory cells on a row-by-row basis, and the CBLs of each port may allow data states to be written to or read from accessed memory cells on a column-by-column basis.
As memory devices get larger, longer WLs may be needed. Longer WLs may degrade the speed of the memory device. For example, if an SRAM multiplexer is greater than eight cells, the height of an Input/Output (IO) cell may tend to be shorter than a control block that could lead to an aspect ratio that may cause layout difficulty and wasted area on a chip. Such an aspect ratio may not be good for placement in the chip. Because the bit cell width may be larger than the bit cell height, the width of a macro containing the memory device may tend to be larger than the macro's height.
Embodiments of the disclosure, for example, may split a conventional 256×288 memory device into two 256×144 segments arranged one over the other. The BLs from a top segment may go over a bottom segment in an upper metal layer. Two word lines in the memory device may be activated in one cycle. One IO for 8 or 16 columns, for example, in a conventional systems may become two IOs for the 8 or 16 columns. The height of the IO circuit may become taller, which is desirable for the macro layout floor plan. The WL lengths, for example, of 288 cells may become 144 cells, thus greater efficiency and faster speeds may be allowed with the shorter WL lengths.
The disclosed embodiments may be faster than conventional systems because of the faster WL assertion. This may provide a faster speed, smaller area for multiplexers, a better aspect ratio, and easier timing design for global-Y signals. The disclosed embodiments may include, for example, an SRAM macro device with a flying BL scheme. The memory of the macro may be split into two segments with one being disposed over the other. Two WLs, one in a bottom segment and another in a top segment, may be activated in a cycle.
As shown in
First segment 102 may comprise a first plurality of memory cells, a first WL 114, and a first BL 116. Similarly, second segment 104 may comprise a second plurality of memory cells, a second WL 118, and a second BL 120. First plurality of memory cells and second plurality of memory cells may comprise, but are not limited to, SRAM cells and Dual Port (i.e., multiport) SRAM cells. Consistent with embodiments of the disclosure, BLs (e.g., first BL 116) from a top segment (e.g., first segment 102) may go over a bottom segment (e.g., second segment 104) in an upper metal layer. First BL 116 from first segment 102 may go over second segment 104 in the upper metal layer, for example, using a “flying BL” scheme.
Two word lines (i.e., a WL_TOP (e.g., first WL 114) and a WL_BOT (e.g., second WL 118)) in memory macro system 100 may be activated in one cycle. For example, one IO for 8 or 16 columns in conventional systems may become two IOs (e.g., first IO circuit 110 and second IO circuit 112) for the 8 or 16 columns with embodiments of the disclosure. The height of the IO circuit with embodiments of the disclosure may become taller as compared to conventional systems, which may be desirable for the layout floor plan of memory macro system 100.
Consistent with embodiments of the disclosure, the WL lengths (i.e., the length of first WL 114 and the length of second WL 118) may become shorter as compared to conventional systems. For example, as shown in
The memory cell 130 includes PMOS transistors 140 and NMOS transistors 142 connected between supply voltage and ground terminals to form cross-coupled inverters. Based on a received memory address, access NMOS transistors 144 selectively connect the outputs of the inverters to the complementary BLs 116A, 116B. WL 114 is connected to gate terminal of access transistors 144 to selectively couple the outputs of the inverters to the BLs 116A, 116B in response to WL select signals transmitted via WLs 114. The cross coupled inverters of memory cell 130 provide two stable voltage states denoting logic values 0 and 1. Metal-Oxide Semiconductor Field Effect Transistors (MOSFETs) are typically used as transistors 140, 142, 144 in memory cell 130. In some embodiments more or fewer than 6 transistors may be used to implement memory cell 130. In the illustrated embodiment, BLs (e.g., first BL 116) from top segment 102 may go over bottom segment 104 in an upper metal layer of the macro 100.
In the example of
Two word lines (i.e., a WL_TOP (e.g., first WL 114) and a WL_BOT (e.g., second WL 118)) in memory macro system 100 may be activated in one cycle. For example, both WL driver circuits 108A, 108B may output WL select signals in response to received memory cell addresses.
Further, as shown in
Tracking BL circuit 300 may comprise a first BL tracking circuit 305, a second BL tracking circuit 310, and a ring oscillator 315 to provide different clock pulse widths for top and bottom segments 102, 104. First BL tracking circuit 305 may correspond to first segment 102 and second BL tracking circuit 310 may correspond to second segment 104. A BL tracking scheme performed for second segment 104 by second BL tracking circuit 310 may be faster than a BL tracking scheme performed for first segment 102 by first BL tracking circuit 305. For example, as shown in
Accordingly, embodiments of the disclosure may include address inputs that may be separated for first segment 102 and second segment 104 such that WLs 114 and 118 for top and bottom segments 102, 104 may asserted based on respective address signals in a single memory cycle. Consequently, embodiments of the disclosure may provide control circuit 106 that may be configured to independently address first WL 114 and second WL 118.
In the example of
Illustrated method 600 includes an operation 610 where first segment 102 comprising the first plurality of memory cells 130A may be provided. For example, the first plurality of memory cells may comprise DP SRAM or multiport SRAM. The first plurality of memory cells 130A may be arranged, for example, in 144 columns and 256 rows.
From the operation 610, where first segment 102 comprising the first plurality of memory cells 130A is provided, illustrated method 600 advances to an operation 620 where second segment 104 comprising the second plurality of memory cells 130B may be provided. The second plurality of memory cells 130A may comprise DP SRAM or multiport SRAM. The second plurality of memory cells may be arranged, for example, in 144 columns and 256 rows. For example, first segment 102 may be positioned over second segment 104. First BL 116 from first segment 102 may go over second segment 104 in the upper metal layer, for example, using a “flying BL” scheme.
Once second segment 104 comprising the second plurality of memory cells is provided in operation 620, method 600 may continue to an operation 630 where a memory address is received, such as by the control circuit 106. In an operation 640, a first WL 114 corresponding to the first segment 102 is activated based on the memory address. Further, in an operation 650, a second WL 118 corresponding to the second segment 104 is activated based on the memory address. In the illustrated method 600, the first WL 114 and the second WL 118 are activated in one cycle. For example, embodiments of the disclosure may provide greater efficiency and faster speeds over conventional systems because the lengths of first WL 114 and second WL 118 are shorter than one long conventional WL.
Embodiments of the disclosure may split a conventional memory device into two segments arranged one over the other. The BLs from a top segment may go over a bottom segment in an upper metal layer in a flying BL scheme. Two word lines corresponding to both the first segment and the second segment in the memory device may be activated in one cycle. Because the WL lengths of embodiment of the disclosure may become shorter, embodiment of the disclosure may provide greater efficiency and faster speeds over conventional systems with the shorter WLs.
An embodiment of the disclosure may comprise a memory macro system. The memory macro system may comprise a first segment, a second segment, a first WL, and a second WL. The first segment may comprise a first plurality of memory cells. The second segment may comprise a second plurality of memory cells. The first segment may be positioned over the second segment. The first WL may correspond to the first segment and the second WL may correspond to the second segment. The first WL and the second WL may be configured to be activated in one cycle.
Another embodiment of the disclosure may comprise a memory macro system. The memory macro system may comprise a first segment, a second segment, and a first BL. The first segment may comprise a first plurality of memory cells. The second segment may comprise a second plurality of memory cells. The first segment may be positioned over the second segment. A plurality of first BLs is coupled to the first plurality of memory cells, and a plurality of second BLs is coupled to the second plurality of memory cells. The first BL may go over the second segment in a flying BL scheme. A first multiplexer is coupled between the plurality of first BLs and a first IO circuit, and a second multiplexer is coupled between the plurality of second BLs and a second IO circuit. Yet another embodiment of the disclosure may comprise a method in which a first segment comprising a first plurality of memory cells is provided. In addition, embodiments of the disclosure may comprise providing a second segment comprising a second plurality of memory cells wherein the first segment is positioned over the second segment. A memory address is received, and a first WL corresponding to the first segment is activated based on the memory address. Additionally, a second WL corresponding to the second segment is activated based on the memory address. Moreover, the first WL and the second WL may be configured to be activated in one cycle.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
Lin, Chih-Yu, Chen, Yen-Huei, Fujiwara, Hidehiro, Pan, Hsien-Yu, Zhao, Wei-Chang
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